Terry Given said:
Firstly, it didnt oscillate at all. during troubleshooting I noticed the >
10M feedback resistor burnt my finger. oops, brown-green-black (someone
put a whole roll of 1R5 into the 10M bin).
I was building a direct-coupled tube amplifier. I needed a 1M to 470k (or
so) voltage divider to bias the first stage.
Oh yeah, circuit is here. Not the greatest of things, but it works. I
think (I gave it away and it hasn't come back yet, so...).
http://webpages.charter.net/dawill/Images/Active Preamp.gif
(Hm, 680k is 1M || 2.2M or 470+220k, I forget which I ended up with.)
Anyways, I wired it up, turned it on, was poking around with the voltmeter,
and nothing was right. It's like all the voltages were too high or too
close (saturated), or something. A grid or two was apparently positive. On
closer inspection, it turned out I had brown-green-black instead of
brown-black-green for that grid bias resistor!
Fortunately, tubes don't mind this treatment at all, despite there being
200V behind the 15 ohm resistor. Gotta love it
My oldest brother (who was working with me on this) claims he will continue
to haunt me with this case of mistaken identity. ;-)
I'm not done here yet. The funniest thing I can think of concerning "15
ohms" is a friend I was voice-chatting with; I casually mentioned 15 ohms
and he suddenly went stern and starting laughing a bit. I was then ROTFL
;-)
Tim (who still doesn't know why he bought that pack of 15R's)